Franz Joseph Haydn[1] (March 31 or April 1, 1732 – May 31, 1809) was a leading composer of the Classical period, called the "Father of the Symphony" and "Father of the String Quartet".

A life-long resident of Austria, Haydn spent most of his career as a court musician for the wealthy Eszterházy family on their remote estate. Being isolated from other composers and trends in music until the later part of his long life, he was, as he put it, "forced to become original".

Joseph Haydn was the brother of Michael Haydn, himself a highly regarded composer, and Johann Evangelist Haydn, a tenor.

Evolution of Haydn's style
Haydn's early work dates from a period in which the compositional style of the High Baroque (seen in Bach and Handel) had gone out of fashion. This was a period of exploration and uncertainty, and Haydn, born 18 years before the death of Bach, was himself one of the musical explorers of this time. An older contemporary whose work Haydn acknowledged as an important influence was Carl Philipp Emanuel Bach.

Tracing Haydn's work over the five decades in which it was produced (roughly, 1749 to 1802), one finds a gradual but ever increasing complexity and musical sophistication, which developed as Haydn learned from his own experience and that of his colleagues. Several important landmarks have been observed in the evolution of Haydn's musical style.

In the late 1760s and early 1770s Haydn entered a stylistic period known as "Sturm und Drang" (storm and stress). This term is taken from a literary movement of about the same time, though some scholars believe that Haydn was unaware of this literary development and that the change in his compositional style was entirely of his own making. The musical language of this period is similar to what went before, but it is deployed in work that is more intensely expressive, especially in the works written in minor keys. Some of the most famous compositions of this period are the "Farewell" Symphony No. 45, the Piano Sonata in C minor (Hob. XVI/20, L. 33), and the six string quartets of Op. 20 (the "Sun" quartets), all dating from 1772. It was also around this time that Haydn became interested in writing fugues in the Baroque style, and three of the Op. 20 quartets end with such fugues.

Following the climax of the "Sturm und Drang", Haydn returned to a lighter, more overtly entertaining style. There are no quartets from this period, and the symphonies take on new features: the first movements now sometimes contain slow introductions, and the scoring often includes trumpets and timpani. These changes are often related to a major shift in Haydn's professional duties, which moved him away from "pure" music and toward the production of comic operas. Several of the operas, such as Il Mondo della luna (The World of the Moon), were Haydn's own work; these are seldom performed today. Haydn sometimes recycled their overtures as symphony movements, which helped him continue his career as a symphonist during this hectic decade.

In 1779, an important change in Haydn's contract permitted him to publish his compositions without prior authorization from his employer. This may have encouraged Haydn to rekindle his career as a composer of "pure" music. The change made itself felt most dramatically in 1781, when Haydn published the six string quartets of Opus 33, announcing (in a letter to potential purchasers) that they were written in "a completely new and special way". Charles Rosen has argued that this assertion on Haydn's part was not just sales talk, but meant quite seriously; and he points out a number of important advances in Haydn's compositional technique that appear in these quartets, advances that mark the advent of the Classical style in full flower. These include a fluid form of phrasing, in which each motif emerges from the previous one without interruption, the practice of letting accompanying material evolve into melodic material, and a kind of "Classical counterpoint" in which each instrumental part maintains its own integrity. These traits continue in the many quartets that Haydn wrote after Opus 33.

In the 1790s, stimulated by his England journeys, Haydn developed what Rosen calls his "popular style", a way of composition that, with unprecedented success, created music having great popular appeal but retaining a learned and rigorous musical structure. An important element of the popular style was the frequent use of folk or folk-like material, as discussed in the article Haydn and folk music. Haydn took care to deploy this material in appropriate locations, such as the endings of sonata expositions or the opening themes of finales. In such locations, the folk material serves as an element of stability, helping to anchor the larger structure. Haydn's popular style can be heard in virtually all of his later work, including the twelve London symphonies, the late quartets and piano trios, and the two late oratorios.

The return to Vienna in 1795 marked the last turning point in Haydn's career. Although his musical style evolved little, his intentions as a composer changed. While he had been a servant, and later a busy entrepreneur, Haydn wrote his works quickly and in profusion, with frequent deadlines. As a rich man, Haydn now felt he had the privilege of taking his time and writing for posterity. This is reflected in the subject matter of The Creation (1798) and The Seasons (1801), which address such weighty topics as the meaning of life and the purpose of humankind, and represent an attempt to render the sublime in music. Haydn's new intentions also meant that he was willing to spend much time on a single work: both oratorios took him over a year to complete. Haydn once remarked that he had worked on The Creation so long because he wanted it to last.

The change in Haydn's approach was important in the history of music, as other composers soon were following his lead. Notably, Beethoven adopted the practice of taking his time and aiming high. As composers were gradually liberated from dependence on the aristocracy, Haydn's late mode of work became the norm in Classical composition.